Abstract

Background

Arterial spin labeling magnetic resonance imaging (ASL-MRI) has been recognised as
a valuable method for non-invasive assessment of cerebral blood flow but validation
studies regarding quantification accuracy by comparison against an accepted gold standard
are scarce, especially in small animals. We have conducted the present study with
the aim of comparing ASL flow-sensitive alternating inversion recovery (FAIR)-derived
unidirectional water uptake (K1) and 68Ga/64Cu microsphere (MS)-derived blood flow (f) in the rat brain.

Methods

In 15 animals, K1and f were determined successively in dedicated small animal positron emission tomography
and MR scanners. The Renkin-Crone model modified by a scaling factor was used for
the quantification of f and K1.

Results

Below about 1 mL/min/mL, we obtain an approximately linear relationship between f and K1. At higher flow values, the limited permeability of water at the blood brain barrier
becomes apparent. Within the accessed dynamic flow range (0.2 to 1.9 mL/min/mL), the
data are adequately described by the Renkin-Crone model yielding a permeability surface
area product of (1.53±0.46) mL/min/mL.

Conclusion

The ASL-FAIR technique is suitable for absolute blood flow quantification in the rat
brain when using a one-compartment model including a suitable extraction correction
for data evaluation.